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Most recent fixed-point filtering operation report


rlog = qreport(h)


rlog = qreport(h) returns the logging report stored in the filter object h in the object rlog. The ability to log features of the filtering operation is integrated in the fixed-point filter object and the filter method.

Each time you filter a signal with h, new log data overwrites the results in the filter from the previous filtering operation. To save the log from a filtering simulation, change the name of the output argument for the operation before subsequent filtering runs.


qreport requires Fixed-Point Designer™ software and that filter h is a fixed-point filter. Data logging for fi operations is a preference you set for each MATLAB session. To learn more about logging, LoggingMode, and fi object preferences, refer to fipref in the Fixed-Point Designer documentation.

Also, you cannot use qreport to log the filtering operations from a fixed-point Farrow filter.

Enable logging during filtering by setting LoggingMode to on for fi objects for your MATLAB session. Trigger logging by setting the Arithmetic property for h to fixed, making h a fixed-point filter and filtering an input signal.

Using Fixed-Point Filtering Logging

Filter operation logging with qreport requires some preparation in MATLAB. Complete these steps before you use qreport.

  1. Set the fixed-point object preference for LoggingMode to on for your MATLAB session. This setting enables data logging.

  2. Create your fixed-point filter.

  3. Filter a signal with the filter.

  4. Use qreport to return the filtering information stored in the filter object.

qreport provides a way to instrument your fixed-point filters and the resulting data log offers insight into how the filter responds to a particular input data signal.

Report object rlog contains a filter-structure-specific list of internal signals for the filter. Each signal contains

  • Minimum and maximum values that were recorded during the last simulation. Minimum and maximum values correspond to values before quantization.

  • Representable numerical range of the word length and fraction length format

  • Number of overflows during filtering for that signal.


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This example shows how to use qreport to log the results of filtering a sinusoidal signal with a fixed-point direct-form FIR filter, firFilt. To use the qreport, set the LoggingMode of fixed-point objects to 'on'.

hd = design(fdesign.lowpass,'equiripple');
hd.arithmetic = 'fixed';
hd.InputWordLength = 32;
fs = 1000;          % Input sampling frequency.
t = 0:1/fs:1.5;     % Signal length = 1501 samples.
x = sin(2*pi*10*t); % Amplitude = 1 sinusoid.
y = filter(hd,x); 
rlog = qreport(hd)
rlog = 
                                                  Fixed-Point Report                                          
                      Min              Max       |              Range              |      Number of Overflows
         Input:              -1                1 |         -65536            65536 |              0/1501 (0%)
        Output:        -1.02325          1.02325 |        -131072           131072 |              0/1501 (0%)
       Product:     -0.48538208       0.48538208 |         -32768            32768 |             0/64543 (0%)
   Accumulator:      -1.0852075        1.0852075 |        -131072           131072 |             0/63042 (0%)

Restore the default logging mode preference.

Introduced in R2011a